Microwave-assisted extraction, SPE and Florisil purification for chromatographic analysis of polycyclic aromatic hydrocarbons (PAHs) in ground roasted coffee

Polynuclear aromatic hydrocarbons (PAHs) are ubiquitous organic compounds, whose occurrence in food may be due to environmental contamination, processing or domestic cooking methods. They are toxic compounds with mutagenic and carcinogenic potential, especially the highly carcinogenic benzo-[a]-pyrene wich presence as been reported in several foods. Foods are controlled in the EU through maxima residual limits (MRLs) of pollutants which stipulate the amounts permitted to appear in foods; there is a Europen Reg. n. 1881/2006 limiting the presence of benzo-[a]-pyrene to 1-10 μg/Kg depending on food category, although coffee is not taken into consideration. The presence of PAHs in coffee samples has been reported and may be attributed to either contamination of the initial green beans or formation of these compounds during the roasting step. This technological treatment modifies coffee chemical composition with the production, changing or decomposition of several compounds. Apart from the particular analytical method applied, the principal problems related to PAHs determination in foods, and in ground coffee as well, are the low detection levels required and the diversity of potential interferences present in this food matrix. Therefore, it is of prime importance to develop analytical methods for their accurate determination in order to estimate the total amount of human exposure to PAHs. This paper presents a sensible, accurate and precise method for microwave-assisted extraction, SPE purification and analytical determination by HPLC-RF of 15 US EPA listed PAHs in ground coffee samples. From the analysis of the obtained data is possible to underline that the considered ground coffee samples contain PAHs concentrations ranging between 12.50 e 42.09 μg/Kg. Among different compounds, phenantrene and pyrene are the most present although they are not considered toxic; while the concentration of toxic molecules such as benzo-[a]-pyrene varies between 0.05-0.43 μg/Kg which is in line with the study of Houessou et al. about ground coffee and the European limits proposed.